This invention relates to a cylinder head arrangement having a basic housing fitted onto a cylinder block, a bucket tappet housing and a cover on the basic housing.
German Patent Document DE 41 16 942 C1 shows a cylinder head arrangement of the above-mentioned type in which a basic housing is fitted onto the cylinder block and is screwed together with it. The basic housing has pulled-up or drawn-up outer walls onto which a hood-type cover is placed. In the interior space formed by the cylinder head cover and the pulled-up outer walls of the basic housing, a bucket tappet housing is arranged at a distance from the outer walls and is screwed to the basic housing. The bucket tappet housing is constructed in several parts and, in a basic element, has the guides of the valve buckets and the lower bearing bracket halves for the bearing of the camshafts. Separate upper bearing bracket halves are placed on these lower bearing bracket halves and are screwed to the bottom parts.
From Volvo Service Manual No. TP 317 14/2, Page 11, a cylinder head for engine Model B6304 is known in which the basic housing placed on the cylinder block is constructed in one piece with the bucket tappet guide and the bottom parts of camshaft bearings. A cylinder head cover, which carries the upper parts of the bearing, are placed onto this basic housing.
For achieving an optimal material structure which has a high strength particularly on the combustion chamber side, it is desirable that this be achieved by a casting process which is largely free of undercuts, as is possible, for example, by means of the type-forming prior art. However, in this case, the construction of the bucket tappet housing according to the prior art which is screwed to the basic housing requires high mounting expenditures caused by the plurality of screwed connections. Also, there are high manufacturing and repair expenditures because of the bearing of the camshafts in the bucket tappet housing-because, during the manufacturing, these bearings bores require a firm reference between the bucket tappet housing and the basic housing. A firm assignment between the bucket tappet housing and the basic housing is therefore also required during the repair and during the exchange.
It is therefore an object of the invention to improve a cylinder head arrangement of the above-mentioned type in that a high-strength material structure, particularly of the basic housing, can be achieved, in that the whole cylinder head arrangement has a high overall stiffness and is easy to manufacture and to mount.
According to the invention, this object is achieved by a basic housing having charge cycle ducts and valve guides, said basic housing fitting on an engine cylinder block,
a bucket tappet housing placed on the basic housing, PA1 and a cylinder head cover which covers cam shafts disposed in two part bearing brackets, PA1 wherein the bucket tappet housing is arranged in a space formed by the basic housing and the cylinder head cover, PA1 wherein the bucket tappet housing is constructed in one piece, PA1 wherein lower bearing bracket halves of the two-part bearing brackets are integrated in the basic housing, PA1 and wherein upper bearing bracket halves of the two-part bearing brackets are constructed at least partially in the cylinder head cover.
Additional advantageous developments of the invention are described herein.
If, in the case of such a cylinder head arrangement, the bearing of the camshafts takes place between the basic housing and the cylinder head cover and the bucket tappet housing is constructed in one piece and is used only for guiding the valve buckets, structural members are obtained which are easy to manufacture and mount and which have a high overall stiffness in the mounted condition. The assembly of the three individual elements, including the basic housing, the bucket tappet guide housing and the cylinder head cover can in this case take place by means of a small number of screwed connections. At the same time, this arrangement results in a very compact construction of the cylinder head arrangement which has a relatively low height for a cylinder head with overhead camshafts and bucket tappets and mainly as a narrow width. In the case of such a construction of the cylinder head arrangement, the cylinder head cover and the bucket tappet housing may be manufactured, for example, as die-cast components. The basic housing of the cylinder head arrangement can advantageously be produced by permanent-mold casting in which case only the ducts (in the case of a water-cooled cylinder head) which are required for guiding the water must be produced by means of molding sand or similar casting or molding techniques. At the same time, by means of this three-part construction of the cylinder head arrangement, only a single junction plane is obtained which must be sealed off to the outside so that a discharge of oil can be prevented by comparatively simple means.
The overall stiffness of the cylinder head arrangement in the mounted condition can be increased advantageously when the bearing brackets are each connected with adjoining outer walls; that is, when the upper bearing bracket halves are connected with the respective adjoining outer wall of the cylinder head cover and the lower bearing bracket halves are connected with the respective adjoining outer wall of the basic housing.
For producing the cylinder head arrangement, important simplifications are obtained if the connection between the cylinder head cover and the basic housing is situated in a junction plane and this junction planes coincides with the junction plane of the bearing bracket halves.
The mounting of the cylinder head arrangement can be considerably simplified when the screwed connection between the cylinder head cover and the basic housing takes place at least in the area of the cylinder bores by the screwing-together of the bearing bracket halves. This results in a considerable reduction of the screwed connection points. At the same time, the width of the cylinder head arrangement is reduced because in the outer area no more screwed connections are required for the purpose of this joining.
A favorable, high-strength screwed connection is obtained between the cylinder head arrangement and the cylinder block if, for each cylinder, four cylinder screws are provided which are disposed around the cylinder bore in a rectangular arrangement. In this case, it is advantageous if, in the case of a sufficient space between the respective cylinders, as occurs, for example, in the case of horizontally opposed engines, one bearing bracket is in each case arranged between two cylinder screws of the adjoining cylinder bores.
The manufacturing and mounting of the camshaft bearing is considerably simplified if, on a face of the cylinder head arrangement, the bearing of the respective camshaft takes place by means of an individual bearing bracket. By means of these individual bearing brackets, when the camshafts are mounted, the pressing-down may take place against the effect of the valve springs. It is particularly advantageous for the construction and manufacturing of the camshaft bearing if the axial guiding of the camshafts takes place by means of these individual bearing brackets.
The arrangement of the individual bearing brackets advantageously takes place in the area of the chain cases required for the drive of the camshafts. The bores of the camshaft bearing may then be carried out from the opposite face of the cylinder head arrangement so that, during the mounting of the camshafts, these openings in the face may at the same time be used as an engagement device for a tool for pressing down the camshafts.
The connection between the bucket tappet housing and the basic housing advantageously takes place in a junction plane into which ducts for the guiding of oil may be cast in a manner which is advantageous with respect to manufacturing techniques. Thus, the required bore expenditures for the guiding of the oil can be considerably reduced. By way of these cast oil ducts, the lubrication of the valve buckets and of the camshaft can take place by means of a few bores.
The manufacturing as well as the sealing of the cylinder head arrangement can be improved if the shaft which leads into the combustion chamber and is used for receiving a spark plug or an injection device, is lengthened and sealed off by means of a sleeve which is inserted between the bucket tapped housing and the cylinder head arrangement. This sleeve can be inserted in a simple and easily mountable manner into a ring-shaped projection in the bucket tappet housing and can be sealed off.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.